I am trying to calculate the angle between two latitudes and longitudes but I am getting wrong result of atan2(X,Y) when used on Excel.

β = atan2(X,Y) = atan2(0.05967668696, -0.00681261948)

It should be 1.68radian (96.51°) but on excel it is showing -0.113666736 (-6.512624235°)

β = atan2(X,Y),

where, X and Y are two quantities and can be calculated as:

• X = cos θb * sin ∆L

• Y = cos θa * sin θb – sin θa * cos θb * cos ∆L

  Latitude/Longitude(1): (Lat1,Lon1)= 39.099912, -94.581213

  Latitude/Longitude(2): (Lat2,Lon2)= 38.627089, -90.200203

  ‘L’ be the longitude,
  ‘∆L=lon2-lon1’ be the difference of longitude,
  ‘θ’ be latitude,
  ‘β‘ be Bearing

3

2 Answers

The problem is that excel uses the function Atan2(y,x) rather than (x, y). In C, Atan2 uses parameters (x, y) which will give you the answer you expected. Just switch your parameters.

A good six years too late on the answer, but hopefully someone finds this useful lol.

1

1. There is nothing wrong with atan2(X,Y) function in Excel: the point you have specified '(0.05967668696, -0.00681261948)' lies in the fourth quadrant, i.e. its angle is really '-6.51°'.

2. But if you want calculate an 'absolute' value of angle between two geographical points, you should use and absolute difference between coordinates:

    β=ATAN2(ABS(0.05967668696), ABS(-0.00681261948))

3. Bear in mind that if this calculation is on a sphere (Earth), it is an approximation because of circular triangle. It is OK for small angles.

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